Molecular medicine holds much promise for advancing cancer diagnosis and treatment if biomarkers, molecular targets and drug effects on these targets can be accurately assessed in tumors. The amount and function of molecular drug targets within signal transduction pathways are often regulated by rapid enzymatic reactions in response to physiological stimuli. Biopsies play a central role in assessing biomarkers and molecular targets in solid tumors, but the traumatic process of cutting tissue samples by current biopsy devices perturb the tumor environment and thereby induce extraneous and confounding molecular responses to tissue trauma, bleeding and ischemia. Expeditious processing of the biopsy specimen using snap freezing or rapid fixation following tissue harvesting may be ineffective for preventing many rapid enzymatic modifications, because time frames of biopsy procedures and tissue handling before they are processed in the lab are longer than that of the enzymatic reactions. Commonly used chemical stabilization of the tissue, for example by formalin, kills the cells and degrades many of the cellular ingredients such as proteins, DNA, RNA, peptides and other molecules.
A method for tumor biopsy that preserves the molecular profile may facilitate pharmacodynamic assessment of targeted therapeutics and may also enable individualized molecular therapy of solid tumors based on accurate information about signal transduction pathways, molecular drug targets and biomarkers. This can maximize the efficacy of new directed chemotherapy agents by choosing the most appropriate patients for each type of therapy. As most of these therapies are associated with severe adverse effects and are highly expensive, individually directed therapy may eliminate suffering in patients that will not benefit from these therapies and can substantially reduce healthcare costs.
Many cancer patients do not benefit from the systemic treatments they receive. For example, an adjuvant chemotherapy regimen that is considered highly effective may often improve the disease-free or overall survival rate by only a few percent. Also, chemotherapy for metastatic disease often provides sustained benefit for a small portion of the patients treated. Therefore, the medical therapies currently available to clinical practice expose far more patients than will benefit to the cost and toxicity of these agents. Although this over treatment is understandable in dealing with life-threatening diseases, the ability to better personalize treatment decisions could have important benefits for patients as well as reduce medical costs.
Biomarkers can be classified into two classes based on their mode of analysis: 1. Histology-based biomarkers adhere to specific structures in the tissue (e.g. cell membranes, chromosomes) and thus require intact tissue (e.g. immunohistochemical (IHC) and fluorescent in-situ hybridization (FISH)). In these tests tissue fixation can be done by chemicals (e.g. formalin-fixed paraffin-embedded, FFPE) or by freezing (e.g. frozen sections). However, freezing adversely affects the ultrastructure of the tissue and cells due to formation of ice crystals, and as such, optical microscopy should be done on fresh or on FFPE tissue samples. These techniques can identify single or groups of cancerous cells in otherwise healthy tissue and may enable early detection of cancer. 2. Content-based biomarkers are determined as the tissue concentration of specific molecules (e.g. proteins, peptides, RNA and DNA, metabolites) that either have altered structure (e.g. DNA alterations) or abnormal levels in tumor cells. These biomarkers do not require the use of intact tissue, and typically involve tissue homogenate that is achieved by sample pulverization in the lab. It would be advantageous to have a biopsy system which enables preservation of biomarkers as well as preservation of the tissue and cellular ultrastructure that provide the basis for histopathology analysis of stained tissue by high magnification microscopy.
A cryogenic biopsy device is disclosed in U.S. Pat. No. 6,551,255. The device is configured for securing and coring of tumors within the body. An adhesion probe provides a coolant for adhering to the tumor and easing attachment of the tumor to the probe. However, the device disclosed therein does not disclose a system and method for providing samples of tissue which may be analyzed histologically as well as via biomarker analysis while maintaining the molecular profile of the sample.
Furthermore, while pathologists use frozen tissue for rapid intraoperative diagnosis, there are limitations to what can be seen in frozen tissue during detailed histologic evaluation. For example, retraction artifacts in tissue that has been frozen might cause problems in the assessment of invasion and in the differential diagnosis of lymphovascular invasion. Also, nuclear details that are needed for tumor grading are lost by ice crystal formation in frozen tissue. These problems may exist in any tissue that has ever been frozen even if it has been immediately fixed in formalin. While freezing the tissue in-situ, before it is cut by the biopsy device, maintains the in-vivo biomarker profile of the tissue and enables histology-based biomarker tests like IHC and FISH, it is not acceptable for detailed histopathology diagnosis. Thus there is a need for a system and method for harvesting and preservation of tissue samples that maintains the fine structural details of the tissue and intracellular components on one hand and the in-vivo biomolecular profile on the other hand.